Heat-development light-sensitive material is known in the art, and heat-development light-sensitive materials and their processes are described, for example, in "Shashin Kogaku no Kiso (Higinen Shashin-hen)" (published by Korona-sha, 1982), pages 242 to 255, and in U.S. Pat. No. 4,500,626.
Further, methods wherein, for example, dye images are formed by the coupling reaction of the oxidized product of a developing agent with a coupler are described, for example, in U.S. Pat. No. 3,761,270 and U.S. Pat. No. 4,021,240. Furthermore, methods for forming positive color images by the light-sensitive silver dye bleach process are described, for example, in U.S. Pat. No. 4,235,957.
Further, recently, the method wherein a diffusion dye is released or formed imagewise by heat development and the resultant diffusion dye is transferred to a dye-fixing element is proposed. In this method, by changing the type of the dye-providing compound to be used or the type of the silver halide to be used, a negative dye image, as well as a positive dye image, can be obtained. More details are described, for example, in U.S. Pat. No. 4,500,626, U.S. Pat. No. 4,483,914, U.S. Pat. No. 4,503,137, U.S. Pat. No. 4,559,290, JP-A-58-149049 ("JP-A" means unexamined published Japanese patent application), JP-A-60-133449, JP-A-59-218443, JP-A-61-238056, EP-A-220 746 (A2), the Journal of Technical Disclosure ("Kokai Giho") 87-6199, EP-A-210 660 (A2), and the like.
With respect to the method for obtaining a positive color image by heat development, various methods have been proposed. For example, U.S. Pat. No. 4,559,290 proposes a method wherein a so-called DRR compound, which has been formed into an oxidized compound incapable of releasing a dye image, is used under the coexistence with a reducing agent or a precursor thereof. In this method, the reducing agent is oxidized in proportion to the exposure amount of a silver halide by heat development, and the above oxidized compound is reduced with the unoxidized remaining reducing agent, to cause a diffusion dye to be released, to form a positive color image. Further, EP-A-220 746 (A) and the Journal of Technical Disclosure ("Kokai Giho") No. 87-6199 (Vol. 12, No. 22) describe heat-development color light-sensitive materials wherein use is made, as a compound capable of releasing a diffusion dye by the same mechanism, of a compound capable of releasing a diffusion dye by reductive cleavage of the N-X bond, in which X represents an oxygen atom, a nitrogen atom, or a sulfur atom.
Since the heat-development color light-sensitive material can be processed easily and rapidly in comparison with the conventional wet-development light-sensitive material, development can be conducted by means of a small-sized compact apparatus. Accordingly, relatively inexpensive apparatuses as color printers, or color copies of a silver salt color light-sensitive material system, are being developed and sold. To further broaden the application of these apparatuses, it is considered that various improvements are required.
As the exposure light source for these light-sensitive materials, various proposals are made, and as a digital exposure light source, for example, light-emitting diodes (LED), semiconductor lasers (LD), and various fluorescent substances are used. In the case of inexpensive LEDs or the like, scanning exposure is made by using an exposure head having a plurality of arranged elements, for example, to shorten the exposure time. However, in the system wherein exposure is made by using a plurality of elements like this for one light-sensitive layer, there is a problem that uneven density occurs on the image, due to dispersion (scattering) of the amount of light and exposure wavelength among the elements.